Metal tire bead

ABSTRACT

To form a metal bead for a tire, two integral portions of a single length of wire are wound in opposite directions about an axis to form a bundle; and the free ends of the two portions are positioned substantially coaxially and adjacent to each other along the outer periphery of the bundle, and are connected integrally to each other to form a bead with a substantially constant section along its whole length.

CROSS REFERENCE TO RELATED APPLICATION

This application is a Divisional Application of currently pending U.S.patent application Ser. No. 08/942,881, filed on Oct. 2, 1997, now U.S.Pat. No. 5,820,717, the disclosures of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates to a method of manufacturing a metal tirebead.

Metal tire beads normally comprise an annular bundle defined by a singlelength of wire wound substantially into a coil, and having a first andsecond end located along the inner and outer periphery of the bundlerespectively.

Bundles of the above type involve several drawbacks. Firstly, the bundlecomprises an outer turn, which is free with respect to the rest of thebundle and incapable of absorbing any stress; and secondly, thediscontinuity in thickness at each end of the length of wire forming thebundle undoubtedly results in uneven mass distribution about therotation axis of the tire.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method ofmanufacturing a bead designed to overcome the aforementioned drawbacks.

More specifically, it is an object of the present invention to provide amethod of producing a bead having a substantially constant section alongits whole length.

According to the present invention, there is provided a method ofmanufacturing a metal bead for a tire, the bead comprising a bundle inturn comprising a length of wire wound substantially into a coil aboutan axis to impart a toroidal shape to the bundle; and the method beingcharacterized by comprising the steps of determining an intermediatepoint along said length of wire, to define, on the length of wire, twoportions, each of which comprises a first free end and a second endintegral with the second end of the other portion at said intermediatepoint; placing said intermediate point on an outer periphery of asubstantially cylindrical forming core coaxial with said axis; windingsaid two portions substantially into a coil and in opposite directionsabout said core to define the bundle and position said two first ends atan outer periphery of the bundle; and connecting said two first endsintegral with each other.

The present invention also relates to a bead formed using the abovemethod.

According to the present invention, there is provided a metal bead for atire, the bead comprising a bundle in turn comprising a continuouslength of wire wound substantially into a coil about an axis to impart atoroidal shape to the bundle; and being characterized in that saidlength of wire comprises two portions, each of which comprises a firstfree end and a second end integral with the second end of the otherportion at an inner peripheral point of said bundle; said two portionsbeing wound in opposite directions about said axis and as of said innerperipheral point; said first ends being located at an outer periphery ofsaid bundle; and connecting means being provided for connecting said twofirst ends integral with each other.

BRIEF DESCRIPTION OF THE DRAWINGS

A number of non-limiting embodiments of the present invention will bedescribed by way of example with reference to the accompanying drawings,in which:

FIG. 1 shows a view in perspective, with parts removed for clarity, of apreferred embodiment of the bead according to the present invention;

FIG. 2 shows a schematic view of a device for producing the FIG. 1 beadaccording to the method of the present invention;

FIG. 3 shows a schematic view in perspective of a preferred embodimentof the FIG. 2 device;

FIG. 4 shows a plan view of the FIG. 3 device;

FIG. 5 shows an axial section of FIG. 4, in which, for the sake ofsimplicity, part of the device is rotated 90°;

FIGS. 6 to 8 show partial cross sections of three different embodimentsof a detail in FIG. 2;

FIG. 9 shows a plan view of the FIG. 1 bead;

FIG. 10 shows a plan view of a variation of the FIG. 1 bead;

FIGS. 11 and 12 show partial views in perspective of two different waysof completing the beads in FIGS. 1 and 7.

DETAILED DESCRIPTION OF THE INVENTION

Number 1 in FIG. 1 indicates a metal bead for a road vehicle tire (notshown).

Bead 1 is substantially toroidal, and comprises a bundle 2 defined by asingle continuous length 3 of wire wound substantially into a coil aboutan axis 4. More specifically, length 3 of wire comprises two portions 5,6 (FIG. 2), which, in the example shown, are identical and define twohalves of length 3, but which in other embodiments may be of differentlengths. Each portion 5, 6 comprises a first free end 7, and a secondend 8 integral with the second end 8 of the other portion 6, 5 at anintermediate point of length 3 located at an inner peripheral point 9 ofbundle 2. Portions 5 and 6 are wound in opposite directions about axis 4and as of point 9, so that the two first ends 7 are located at an outerperiphery 10 of bundle 2 (FIGS. 9 and 10). In the FIG. 9 embodiment, thetwo ends 7 are coaxial, substantially contact each other, and areconnected integral with each other by means of a weld spot 11.

The FIG. 10 variation shows a bead 1a substantially identical to bead 1,except that the two ends 7, as opposed to being coaxial, are locatedside by side and parallel to each other along respective portions 12,and are connected integral with each other by means of a linear weld 13extending along substantially the whole length of portions 12.

With reference to FIG. 2, bead 1 may be formed by winding portions 5 and6 in opposite directions onto respective spools 14 and 15 so that anintermediate portion 16 of length 3 comprising point 9 is left free;placing portion 16, at point 9, onto the outer periphery of a formingcore 17; and winding portions 5 and 6 in opposite directions about core17 and simultaneously off spools 14 and 15. Length 3 of wire is of sucha length that, when portions 5 and 6 are unwound completely off spools14 and 15, the two ends 7 are located facing and adjacent to each otherfor connection by means of weld spot 11. In the case of bead 1a, on theother hand, length 3 of wire is of such a length that, when portions 5and 6 are unwound completely off spools 14 and 15, the two ends 7 arelocated side by side and parallel to each other for connection by meansof linear weld 13.

As shown in FIGS. 6, 7 and 8, cylindrical forming core 17 comprises adisk--hereinafter referred to as "disk 17" --coaxial with axis 4 anddefined by two plates 18, which are coaxial with each other and withaxis 4, are positioned contacting each other along a mid plane 19perpendicular to axis 4, and are connected to each other by fasteningelements 20 (FIG. 5).

The two plates 18 define a peripheral annular groove 21 having asubstantially U-shaped section and for housing bundle 2. Groove 21 isdefined axially by two shoulders 22, and radially by an undulatedsurface 23, which defines a number of annular recesses for housingrespective turns of bundle 2, and has a section symmetrical with respectto plane 19. More specifically, in the FIG. 6 and 7 variations,undulated surface 23 defines a pair of inner recesses 24 adjacent to,and on either side of, plane 19; and a pair of outer recesses 25 locatedon either side of plane 19, both radially and axially outwards ofrespective recesses 24, and adjacent to respective shoulders 22. In theFIG. 8 variation, on the other hand, a further intermediate recess 26 isprovided between each recess 24 and respective recess 25. The distances,measured parallel to axis 4, between each recess 24, 26, 25 of one plate18 and the corresponding recess 24, 26, 25 of the other plate 18 areequal to whole numbers of diameters of length 3 of wire, which numbersincrease from recesses 24 to recesses 25.

FIGS. 6 to 8 show three different winding sequences, all of whichcommence by simultaneously filling inner recesses 24. More specifically,the sequences shown in FIGS. 6 and 7 are substantially similar, in thateach of portions 5 and 6 is kept on a respective side of plane 19 at alltimes, and the more outer turns formed by each portion 5, 6 aresuperimposed on the respective more inner turn s until bead 2 iscompleted. In the FIG. 8 sequence, on the other hand, the more outerturns formed by each of portions 5 and 6 are offset with respect to themore inner turns, and some of the turns of each of portions 5 and 6 areinserted combfashion between two adjacent turns of the other portion 6,5 and astride plane 19.

The above winding methods are preferably implemented, as shown in FIGS.3, 4 and 5, by means of a winding device 27, wherein disk 17 is fittedto a shaft 28 coaxial with axis 4 and having a first portion 29supporting disk 17, and a second portion 30 connected integral with afixed frame 31.

A tubular body 32, coaxial with axis 4, is mounted for rotation aboutshaft 28, and is fitted integrally with a gear 33 coaxial with axis 4and meshing with a powered gear 34 for rotating gear 33, together withtubular body 32, about axis 4.

Tubular body 32 is fitted idly with a sleeve 35, one end of which isfitted integrally with a bevel gear 36 facing a further bevel gear 37integral with tubular body 32. Gears 36 and 37 are coaxial with eachother and with axis 4, are positioned oppositely conical, and meshsimultaneously with a bevel pinion 38 fitted integrally to one end of ashaft 39, which is fitted idly to a support 40 integral with frame 31,so as to rotate about a respective axis 41 perpendicular to axis 4.Together with pinion 38, gears 36 and 37 define a transmission 42,whereby rotation of gear 36 in one direction corresponds to the samerotation of gear 37 in the opposite direction.

Tubular body 32 and sleeve 35 comprise respective radial arms 43 and 44,which are maintained diametrically opposite by transmission 42, and arefitted idly with respective spools 14 and 15. More specifically, arm 43is connected integrally to the free end of tubular body 32 opposite theend facing frame 31 and fitted with gear 33, and is fitted, at an endportion, with a pin 45, which has an axis 46 parallel to axis 4,projects from arm 43 on the opposite side of arm 43 to frame 31, andidly supports spool 14. Arm 44, on the other hand, is substantiallyC-shaped, and comprises an end portion 47 fitted with a pin 48, whichhas an axis 49 parallel to axis 4, projects from portion 47 towardsframe 31, and idly supports spool 15. Spools 14 and 15 are identical,and are wound in the same direction with respective portions 5 and 6 oflength 3 of wire. As spools 14 and 15, however, are positioned parallelto each other but facing in opposite directions, portions 5 and 6 arewound in opposite directions with respect to the reference constitutedby frame 31.

Each arm 43, 44 is provided, close to respective spool 14, 15, with acontrol device 50 comprising a linear actuator 51 parallel to axis 4 andfitted on the end with a guide roller 52 facing and adjacent to theperiphery of disk 17, and which is engaged by respective portion 5, 6 asthis is unwound off respective spool 14, 15. Device 50 also comprises acentral control unit (not shown) for moving roller 52, and hencerespective portion 5, 6, transversely in a direction parallel to axis 4,and so performing the sequences described previously with reference toFIGS. 6 to 8.

A guide element 53 is also provided between each spool 14, 15 andrespective roller 52, is fitted to respective arm 43, 44, and providesfor directing length 3 of wire correctly from spool 14, 15 towardscontrol device 50.

Operation of device 27 is clearly understandable from the foregoingdescription without any further explanation. By virtue of transmission42 rotating tubular body 32 and sleeve 35 similarly but in oppositedirections about axis 4, operation of gear 34 causes spools 14 and 15 torevolve similarly but in opposite directions about axis 4 and theperiphery of disk 17, so that spools 14 and 15 are gradually unwound togradually form bundle 2 according to one of the sequences described withreference to FIGS. 6 to 8, and as described with reference to FIG. 2.

Once completed, bundle 2 is removed by parting the two plates 18; and,as shown in FIGS. 11 and 12, bundle 2 is then wound either with a strip54 of elastomeric material covering it completely, or with a cord 55 ofheat-shrink material, to secure the turns of bundle 2 to one another.

The bead formed as described above affords the advantage of continuityand, hence, uniformity along the whole of its length. In particular, theabsence of any discontinuity provides for greater resistance to radialstress and greater rigidity of the bead, and also for better balance ofthe relative tire.

I claim:
 1. A metal bead for a tire, the bead comprising a bundle ofwinds in turn including a continuous length of wire wound substantiallyinto a coil about an axis to impart a toroidal shape to the bundle; andbeing characterized in that said length of wire includes two portions,each of which includes a first free end and a second end integral withthe second end of the other portion at an inner peripheral point of saidbundle; said two portions being wound in opposite directions about saidaxis from said inner peripheral point; said first ends being located atan outer periphery of said bundle; said first ends being disposed in theradially outermost winds of the bundle; and connecting means beingprovided for connecting said two first ends integral with each other. 2.A bead as claimed in claim 1, characterized in that said first ends arepositioned coaxial and facing each other.
 3. A bead as claimed in claim2, characterized in that said connecting means comprise a weld spotinterposed between said facing first ends.
 4. A bead as claimed in claim1, characterized in that said first ends are positioned parallel andside by side along respective end portions of a given length.
 5. A beadas claimed in claim 2, characterized in that said connecting meanscomprise a continuous weld extending along said end portions.
 6. A beadas claimed in claim 1, characterized by comprising a reinforcing elementwound about said bundle.
 7. A bead as claimed in claim 6, characterizedin that said reinforcing element is a strip of elastic material.
 8. Abead as claimed in claim 6, characterized in that said reinforcingelement is a cord of heat-shrink material.
 9. A metal bead for a tire,the bead comprising a bundle of winds in turn including a continuouslength of wire wound substantially into a coil about an axis to impart atoroidal shape to the bundle; and being characterized in that saidlength of wire includes two portions, each of which includes a firstfree end and a second end integral with the second end of the otherportion at an inner peripheral point of said bundle; said two portionsbeing wound in opposite directions about said axis from said innerperipheral point; said first ends being located at an outer periphery ofsaid bundle; connecting means being provided for connecting said twofirst ends integral with each other; andsaid bundle having a sectionhaving a plane of symmetry perpendicular to said axis; each said portiondefining turns which are all located on a respective same side of saidplane.
 10. A bead as claimed in claim 9, characterized in that each turnof each said portion is superimposed directly on a corresponding moreinner turn, if such a more inner turn exists.
 11. A metal bead for atire, the bead comprising a bundle of winds in turn including acontinuous length of wire wound substantially into a coil about an axisto impart a toroidal shape to the bundle; and being characterized inthat said length of wire includes two portions, each of which includes afirst free end and a second end integral with the second end of theother portion at an inner peripheral point of said bundle; said twoportions being wound in opposite directions about said axis from saidinner peripheral point; said first ends being located at an outerperiphery of said bundle; connecting means being provided for connectingsaid two first ends integral with each other; andsaid bundle having asection having a plane of symmetry perpendicular to said axis; each saidportion defining turns of which a portion are inserted combfashionbetween two adjacent turns of the other portion and astride said plane.12. A bead as claimed in claim 11, characterized in that each turn ofeach said portion is offset with respect to a corresponding more innerturn, if such a more inner turn exists.